Pyrometer construction



March 28, 1961 s. N. HOWELL 2,976,730

PYROMETER CONSTRUCTION Filed June 7, 1957 FIG. I. Z6? Z9 ,0 I

FIG. 3.

ATTORNEYl PYROMETER CNSTRUCTON Sabert N. Howell, Huntington, N.Y.,assignor to Servo Corporation of America, New Hyde Parli, NX., acorporation of New York Filed .lune 7, 1957, Ser. No. 664,349

6 Claims. (Cl. 731-355) My invention relates to a radiation-pyrometerconstruction, and in particular to improved sighting means for such adevice. Ihis invention incorporates improvements over the inventiondisclosed in Wormser Patent No. 2,761,072 and in patent application,Serial No. 481,124, filed January 11, 1955, in the name of William C.Derganc, now Patent No. 2,920,485.

It is an object of the invention to provide an improved device of thecharacter indicated.

Another object is to provide an improved radiation pyrometerconstruction in which visual sighting may be accomplished withoutparallax error for the infrared responsive element of the system.

A further object is to meet the above objects with a device which lendsitself to interchangeable lenses whereby non-parallax sighting may beavailable regardless of the focal length of the selected lens.

Other objects and Various further features of novelty and invention willbe pointed out or will occur to those skilled in the art from a readingof the following specification and claims in conjunction with theaccompanying drawings. In said drawings, which show, for illustrativepurposes only, a preferred embodiment of the invention:

Fig. 1 is a longitudinal sectional view through a pyrometerincorporating features of the invention;

Fig. 2 is a left-end view of part of the sighting mechanism of Fig. l,certain parts being broken away and shown in section in order toillustrate mounting details for parte;

Figs. 3 and 4 are enlarged fragmentary views taken respectively in theplanes 3-3 and 4 4 of Fig. 2; and

Fig. 5 is a longitudinal sectional view of a lens system interchangeablewith the one shown in Fig. l.

Briefly stated, my invention contemplates an improved infraredradiation-pyrometer construction in which interchangeable focusingelements may be readily adapted to the pyrometer, and yet visualsighting without .parallax error may be achieved with the same system ofsighting parts, regardless of the focal length of the selected focusingelement. The visual-sighting mechanism in connection with which myinvention is described is of the telescopic variety, wherein thetelescope is oriented generally parallel to the infrared-response axisbut offset therefrom, and is mounted, for example, on the exterior ofthe pyrometer housing. The focusing element may be one of a series ofinterchangeable lens systems, each complete with its own lens barrel,said barrel having a forwardly projecting part to which a periscopicadapter is removably attachable. Angular locating parts on the lensbarrel, on the housing, and on the periscopic adapter assure a givenangular orientation of the periscopic adapter, regardless of the lenssystem employed. 'Ihe periscopic adapter includes offsetting mirrors,one of which is on the optical axis, and these mirrors are small so asonly insubstantially to obscure any collected or collectable infraredenergy.

Referring to Fig. 1 of the drawings, my invention nem ice

is shown in application to a radiation pyrometer of the type alreadydescribed in said copending Derganc application. Such a pyrometer iscontained within a generally tubular housing 10 and comprises aninfrared responsive cell or element, such as a thermistor bolometercontained within a capsule 11 and facing generally `in the direction ofone longitudinal end of the housing 10. The optical system may comprisea focusing mirror, but in the form shown, includes a lens 12 of suitableinfraredtransmitting material, such as arsenic-trisultde glass; lens 12faces out the same longitudinal end of the housing and serves to collectradiation on an optical axis 13 and to focus the same on the cell withincapsule 11. For more quantitative measurements, the pyrometer mayinclude a second similar cell within a capsule 14, the capsule 14 beingoriented to face a reference source 15. A chopping device or shutter 16is mounted on a continuously running shaft 17 and serves periodically tointerrupt the incidence of radiation on the cell 11. A similar chopper1S performs the same operation for reference radiations from the source15, incident on the reference cell 14. Both choppers are driven bysuitable means, such as a synchronous motor 19, which may be mounted atthe rear end of the housing. The actual circuitry for processing signalsdeveloped at 11-14 has beendisclosed in other copending applications.

The particular pyrometer of Fig. 1 is of a variety in which the housing10 is particularly adapted to receive interchangeable lenses so that thesame may be caused to image the sensitive area of cell 11 (in varioussizes) at remote locations to be monitored. In the form shown, the lens12 forms part of an interchangeable lens assembly, including anelongated barrel 2li longitudinally slidably received in a suitablyformed bore 21 in a lens adapter'ltting 25 at the forward end of thepyrometer. The inserted lens is shown to be in properly focused positionwhen the inner end of the barrel 20 Strikes a stop or shoulder, as at22; for single-purpose applications, this stopped position may representfixed focus for the desired distance to the unknown source, but forgeneralpurpose use, the stopped position may represent focus at infnity,the focus for intermediate object distances being selectively availableupon slidable adjustment of barrel 20 in bore 21, as by observing theadjustment `against a pre-calibrated range scale (not shown).

For a purpose which will later be clear, I prefer that interengagingangular-locating means shall cooperate between the lens barrel 20 andthe housing 10 so that only one angular orientation shall be availablefor the inserted lens assembly. In the form shown, a key or pin 23 onthe lens barrel rides a longitudinal key-way 24 inthe front tting 25 ofthe housing 10, and a knurled set screw 26 serves to anchor the insertedlens assembly in proper position.

'For relative aperture control, a selected one (55) of a variety ofaperture plates is provided with an upwardly projecting tab 56 formanual insertion in and removal from a suitable slot and guide means inthe barrel 20. When the pyrometer is not in use, the inserted plate 55may be unapertured, thereby providing a cover for lens In accordancewith a feature of the invention, I provide a visual-sighting mechanisminvolving no parallax error, and specifically adapted to interchangeablelenses, as in the case of the lens assembly 12-2ll. Such sightingmechanism may comprise a pair of longitudinally spaced gun-sightelements on the exterior of housing 10 and on a sighting axis generallyparallel to the optical axis 13, but in the form shown I employ anelongated telescope 27 having an eye piece 28, said telescope beingaligned generally parallel to and offset from the optical axis 13,

Suitable clamps or mounting brackets 29 permanently secure the telescope27 in position on the outside of the housing 10.

In order to bring the visual-sighting axis of the telescope 2,7 intocoincidence with the optical axis 13, I provide a periscope attachment36 removably securable to the front end of the lens assembly. In theform shown, the front end is a sunshade 31 of generally expandedcylindrical open form and includes a cylindrical portion 32 adapted tolongitudinally slidably receive the counterbore of the adapter ring 30.Said counterbore defines a shoulder or step 33, whereby an accuratelimit or location may be established for application of the ring and forits alignment on the lens-assembly extension 31. The periscope`attachment 36 includes two inclined mirrors 34-35, one of which (34) isaligned with the optical axis 13 and is of small dimensions so as toallow most of the collected radiant energy to pass the lens 12 forfocusing at 11; the second mirror element (3S) is aligned with thetelescope axis, and the inclination l of both mirrors is such thatxtheir respective reflections of the optical axis and of the telescopeaxis are aligned with each other. Thus, for a substantially 45inclination of both mirrors 34-35, the visual-sighting axis fromtelescope 27 may be made coincident with the optical axis 30, and noparallax error is introduced.

-For accurate alignment of the visual sight 27 with a given pyrometer,it is desirable to provide for certain small angular adjustment inpositioning each of the nn'rrors 34-35 In the form shown, the mirror 34is carnied by a triangular prismatic member 36 mounted on adiametrically extending shaft 37, journaled at diametrically oppositepoints 33--39 in the adapter ring 30. At one of these locations (39),provision is made for adjustment in angular position about the shaftaxis, by mounting a small crank member 40 on the end of shaft 37, and byproviding a set screw 41 to adjust the position of crank 40 against areacting spring 42 (see Figs. 2 and 3).

The other mirror 3S may be similarly mounted for pivoting about stud or`pivot means 43 journaled in Supporting brackets sat- 45 integral withthe attachment ring 30 (see Figs. l and 2). The set screw 46 is shownacting on the prismatic block `47 on which the mirror 35 is carried, andadjustments are made against reaction from a spring 48. An opening 49 inthe forward tubular extension 31 of the lens barrel permits sightingaccess for the radially offset rays between mirrors 34-35.

A third adjustment of mirror position may be provided in the periscopeadapter 30, for purposes of eliminating any possibility of eccentricityin the `alignment of mirror 34. Such adjustment is available at 38 andis shown in detail in Fig. 4, wherein the end of shaft 37 is seen tohave freedom for longitudinal adjustment in an elongated slot 58. Alongitudinally extending set screw S9 adjustably positions the end ofshaft 37 against the reaction from .a compression spring 60, thuspermitting slight trimming adjustment of mirror position -to eliminateeccentricity with respect to optical axis 13.

A set screw 50 serves to secure the attachment ring 30 in place on theextension tube 31, and similar set screws 51-52 may be provided atangularly spaced locations, as desired. In order that the angularlocation of the olfsetting mirrors 34--35 shall be correctly establishedwith respect to the housing 1i), I provide inter-engaging angularlocating means cooperating between the extension 31 of the lens barreland the attachment 30. This is achieved by merely longitudinallyslotting diametrica-lly opposite parts of the forward end of thelens-tube extension 31, as at 53, so as to receive the shaft 37 andenable the shaft 37 to perform the additional function of keying theattachment ring to the lens tube 20 and therefore also to the housing10. Preferably, however, the shanks of set screws 50-51--52 are somewhatpointed, for accurate locating accommodation in counterbored locatingholes, as at 50i-S2 (Fig. l) in the outer cylindrical part 32 of barrel20, thereby relying primarily on set screws 50-5152 for angularlocation, rather than on keyed engagement at 37-53. f

In Fig. 5 I show a different lens assembly having a longer focal lengththan the assembly of Fig. l, but of essentially the same structuralcharacteristics. Thus, the assembly of Fig. 3 may have a more elongatedtubular barrel 20', accommodating a longer focal-length lens 5d, whichmay also be of infrared-transmitting material such as arsenictrisulflde. Angular-locating reference to the periscope adapter 30 isachieved at 53-5G-52, and similar reference to the housing 10 isachieved by key means 23.

It will be seen that I have described a relatively simple attachment fora pyrometer of the character indicated, whereby the pyrometer mayaccommodate interchangeable lenses of various focal lengths and yet mayat the same time provide coaxial alignment of the infraredresponse axiswith that of the visual-sighting means, regardless of the selected lensassembly. The same sighting parts serve all lenses applied to thesystem, and no adjustment of the telescope or of the periscope parts isneeded, regardless of the focal length of the inserted lens, onceinitial adjustments are made at 41-43-59 for the particular telescope 27and adapter 34) of a given pyrometer.

While I have described the invention in detail for the preferred formshown, it will be understood that modifications may be made within thescope of the invention as dened in the claims which follow.

I claim:

l. In a radiation pyrometer, an elongated housing containing aninfrared-responsive element and having at one end an optical systemcollecting infrared radiant energy on an optical axis and focusingcollected energy on said element, said optical system being removablysecured in said housing and said housing being adapted to removablyreceive a selected one of a plurality of similar optical systems ofdiiferent focal lengths for focus on said element, a visual sightingmechanism comprising a telescopic member having an alignment axisgenerally parallel with said optical axis but offset therefrom, and aseparate detachably removable periscopic oifsetting assembly carried bythe front part of said optical system, said periscopic assembly beinggenerally open in the path of energy collected by said optical systemand including a relatively small first inclined mirror on said opticalaxis and a second inclined mirror generally aligned with the telescopeaxis and spaced from said telescopic member, both said mirrors beinginclined to an extent such that their respective reflections from saidaxes are aligned with each other.

2. In a radiation pyrometer, an elongated housing containing an infraredresponsive element on a generally central axis and facing out one end ofsaid housing, a detachably removable lens system responsive to infraredradiation at said end and focusing such radiation on said element, saidlens system including a barrel removably securable at said end of saidhousing, and said barrel including a portion projecting longitudinallybeyond the lens element thereof, visual sighting means supported on theoutside of said housing and having an alignment axis generally parallelto but offset from said optical axis, and a periscope attachmentseparate from said visual sighting means and detachably securable to thefront end of said barrel, said attachment comprising two relativelysmall mirrors, one of said mirrors being aligned with the sightmg axisand spaced in front of said visual sighting means, the other of saidmirrors being aligned with the optical axis, the inclination ofsaid'mirrors being such that the respective reflections of said axes arealigned with each other.

3. A pyrometer according to claim 2, in which said attachment includes amounting ring longitudinally slidably mounted on said barrel, andsecuring means for holding a mounted Vposition of said ring.

4. A pyrometer according to claim 3, in which said mirror on saidoptical axis is mounted on an elongated thin shaft extending generallydiametrically of opposite sides of said ring, means pivotally supportingsaid shaft at said opposite sides, and adjustment means on one of saidsides for securing an adjusted angular position of said shaft about theaxis of said shaft.

5. A pyrometer according to claim 3, in which said mirror on saidoptical axis is mounted on an elongated thin support carried by andextending generally diametrically of opposite sides of said ring, andmeans adjustable longitudinally of said optical axis at one end of saidthin support for adjusting the position of said mirror to eliminateeccentricity of alignment thereof with said optical axis.

6. A radiation pyrometer, comprising an elongated housing containing aninfrared sensitive element facing toward one end of said housing, a lenssystem comprising a lens and an elongated barrel detachably securable atsaid end and including means angularly locating said lens to saidhousing at said end, said lens including an infraredtransmitting lenselement focusing collected radiant energy on said sensitive element whenin inserted secured position, said barrel extending longitudinallybeyond said lens element, a periscopic attachment removably securable tosaid barrel, said attachment comprising a ring longitudinally slidablytting the outer end of said barrel, intertting angular locating means onsaid ring and barrel for assuring that said ring and said housing Willhave a predetermined angular relation when assembled, andan elongatedtelescope carried by said housing and having its `axis orientedgenerally parallel to the optical axis of the lens system, saidperiscope attachment having two spaced offsetting mirrors, one of saidmirrors being aligned with said telescope and the other of said mirrorsbeing aligned with said optical axis.

References Cited in the file of this patent UNITED STATES PATENTS v1,302,254 Warnecke Apr. 29, 1919 1,474,903 Hase Nov. 20, 1923 2,113,450Lasky et al. Apr. 5, 1938 2,122,941 Hufler et al. July 5, 1938 2,761,072Wormser Aug. 28, 1956

